Guidance for Treatment of Airport Stormwater Containing Deicers (2013)

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90 Aerobic Biological Deicer Treatment—Biological treatment processes using aerobic (oxygen- consuming) microorganisms (primarily bacteria) for degrading the primary deicer constituents into smaller molecules. The purpose of aerobic treatment is to reduce the mass loads and concentrations of the primary deicer constituents in stormwater discharged to surface waters, groundwater, or the sanitary sewer. By-products from aerobic deicer treatment systems include wasted biomass and carbon dioxide. Aerobic Mode—Operational mode for the biological respirometer used in the lab study that measures oxygen uptake by microorganisms as pollutants are consumed. Aircraft Deicing Fluids—Deicers and anti-icers applied to aircraft; typically the primary deicer constituent is propylene glycol in the United States and ethylene glycol in Canada. Glycerin is the primary deicer constituent in a few products. Ammonia-Nitrogen—The concentration of nitrogen contained in the compound ammonia in a water sample. Anaerobic Biological Treatment—Biological treatment process using anaerobic microorganisms in the absence of oxygen for degrading the primary deicer constituents in stormwater discharges. By-products from anaerobic treatment include wasted biomass, methane, and carbon dioxide. Anaerobic Mode—Operational mode for the biological respirometer used in the lab study that measures methane production by microorganisms as pollutants are consumed. Attached Biological Growth Treatment—Treatment system where bacterial films form on inert media, such as activated carbon or plastic contained in a reactor. Automatic Diversion System—Stormwater diversion system where a monitor is used to detect pollutant concentration, and an electronic system is used to control the diversion of storm- water based on the levels of pollutant detected by the monitor. Biochemical Oxygen Demand (BOD)—The amount of oxygen used by bacteria to break down organic materials and organic nitrogen. Biogas/Off-Gas—Gas, typically consisting of methane or carbon dioxide, produced from biological digestion of the primary deicer constituents in a treatment system. Biological Inhibition—Decrease in biological activity as a result of environmental factors (e.g., temperature, decreased food source) or exposure to a toxic substance. Bioreactor/Reactor/Reactor Vessel/Biological Reaction Vessel—Tank or basin containing microorganisms that are used to degrade pollutants from a sample stream. Glossary

Glossary 91 Carbon Dioxide (CO2)—A colorless, odorless gas produced as a by-product of aerobic biological treatment. Chemical Oxygen Demand (COD)—The oxygen required for the chemical reaction with organic compounds in a sample. Deicer—Either a liquid or dry chemical applied to melt ice or prevent ice from forming on a surface. In this guidebook, it can refer to either aircraft or pavement deicers or anti-icers. Deicer Treatment—The process of removing deicing chemicals and their derivative products from stormwater. Dissolved Oxygen (DO)—Oxygen that is dissolved in water. Effluent Limits/Collection Efficiency—Any restriction on quantities, discharge rates, and con- centrations of pollutants discharged from point sources. Food Supply/Substrate/Pollutant—Substance consumed by bacteria that provides nutritional support for biological functioning. Industrial Pretreatment Program—A program implemented by the POTW to prevent non- compliance or interference that may occur as a result of industrial-user wastewater discharges into the POTW sewer system. Pretreatment programs for POTWs are required under federal regulations establishing technology-based standards (effluent guidelines) for various industrial categories. Industrial User—A nonresidential user that discharges non-sanitary, industrial-process waste- water into a POTW sewer. An industrial user must comply with the conditions of its discharge permit issued under the POTW’s industrial pretreatment program. Methane (CH4)—A colorless, odorless, flammable gas produced as a by-product of anaerobic biological treatment. Microbe/Microorganism/Biomass/Biomass Culture/Bacteria—The biological media used for treatment in a bioreactor. National Pollutant Discharge Elimination System (NPDES)—U.S. EPA’s program for permitting point-source discharges to waters of the United States. Nutrients—Elements, including nitrogen and phosphorus, that are required for biological organ- isms to grow, and that may lead to excessive growth of algae and other nuisance plants in natural surface water systems. Online Monitor—Permanently mounted devices designed to sample flow streams and analyze the samples on a regular basis without direct involvement of facility staff. Pavement Deicer—Deicers applied to aircraft operations areas. The compounds are typically applied undiluted. The primary deicer constituents are sodium formate, sodium acetate, and potassium acetate. Parameter—A parameter may be a chemical (e.g., ammonia), a physical characteristic (e.g., temperature or flow), or the result of analytical testing (e.g., biochemical oxygen demand). pH—A measure of the acidity or alkalinity of a sample. Primary Deicer Constituent—The primary freezing-point depressant constituents in deicers (propylene glycol, ethylene glycol, glycerin, acetate, formate, urea) that most often drive the need for deicer treatment. Stormwater—Precipitation runoff, including rain and snowmelt.

92 Guidance for Treatment of Airport Stormwater Containing Deicers Stormwater Monitoring—The act of obtaining a quantitative measurement of stormwater characteristics. Surcharge Fee—Fee charged to an industrial user by a municipal treatment plant for wastewater with pollutant concentrations that exceed the typical concentration of sanitary wastewater. Surrogate—A parameter that is measured in place of another parameter. A mathematical relationship exists between the two parameters such that the surrogate parameter’s concen- tration can be used to estimate the desired parameter concentration. Technology-Based Effluent Limit—Uniform national discharge limits established as part of the regulations established under the federal Clean Water Act. The limits are based on the ability of dischargers in the same industrial category to treat discharges. Total Dissolved Solids (TDS)—Organic and inorganic solids that are able to be filtered in a sample. Total Organic Carbon (TOC)—The measurement of carbon dioxide produced during the conversion of all organic carbon in a sample. Total Suspended Solids (TSS)—A class of solids associated with particulates (i.e., sand or silt) that can cause sedimentation in a stream or block light, which will inhibit aquatic life. In analytical terms, organic and inorganic solids suspended in liquid, when filtered, remain on weighted glass-fiber filter paper. Water-Quality–Based Effluent Limit—Discharge limits established as part of the NPDES program to protect the quality of the receiving water. 5-Day Biochemical Oxygen Demand (BOD5)—The oxygen required for the biological degradation of organic compounds in a sample by bacteria and nutrients after 5 days.